This project will address the critical need for real-time, continuous quantification of local tissue perfusion, oxygen tension and temperature in vivo. The feasibility of combining in a miniature hybred thermistor-polarographic oxygen sensor, both the unique capability of the Extended Thermal Diffusion Probe (ETDP) and recent advances in oxygen tension measurements will be investigated. A platinum wire will be encapsulated in the glass coating of a thermistor bad, recessed (electro-) chemically, and gold plated to serve as a flow insensitive oxygen sensor. The ETDP System currently qualifies temperature to plus or minus 0.003 C and perfusion to plus or minus 10% over the range of physiologic flows. The ETDP circuitry and software will be expanded t measure oxygen tension to plus or minus 1 mm/Hg, either in steady state mode or in transient model when additional precision is desired. The long term stability of the hybred sensor will be determined. This integrated system will permit investigation of perfusion, temperature, and oxygen tension (and their interrelationships) in the same tissue volume. This capability is important for many research and clinical studies including determination of the effectiveness of pharmacologic manipulations in different experimental and clinical states of circulatory shock (a condition responsible for 250,000 American deaths arrhythmias, and for monitoring the various forms of thrombolytic therapy for coronary artery occlusion. Following successful demonstration of feasibility Phase II will be devoted to pre-commercial development and evaluation of the integrated system by our Clinical Evaluation Group.